Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting a discovery signal in a wireless communication system.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
Device-to-device (D2D) communication is a distributed communication technique in which adjacent wireless nodes directly deliver traffic. In the D2D communication, a wireless device such as a mobile phone autonomously discovers another wireless device which is physically adjacent, establishes a communication session, and thereafter transmits traffic. The D2D communication can solve a traffic overload problem by distributing traffic concentrated on a base station. The D2D technique such as Bluetooth or WiFi Direct directly supports communication between wireless nodes without a support of the base station.
For the D2D communication, there is a need for a discovery signal for discovering a device for participating in the D2D communication and a synchronization signal for achieving synchronization between D2D devices.